[英]Detect binding property changed within a user control
我正在使用Windows Store应用程序,在其中我有一个用户控件作为flipview内的数据模板。
用户控件:(ImagePage.xaml)
<UserControl
x:Name="userControl"
x:Class="MWC_online.Classes.ImagePage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:MWC_online.Classes"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="768"
d:DesignWidth="1366">
<Grid Background="#FFF0F0F0" Margin="4,0">
...
<Image Source="{Binding Img}" Stretch="None" HorizontalAlignment="Left" VerticalAlignment="Top" />
<StackPanel x:Name="stackPanel" HorizontalAlignment="Left" Margin="984,83,0,0" Width="325">
<Grid Background="{Binding Colour}">
<TextBlock Margin="30,30,30,15" Text="{Binding TextContent1}" FontWeight="Light" TextWrapping="Wrap" Foreground="#FF00ABE8" FontSize="29" />
</Grid>
<Grid Background="{Binding Colour}">
<TextBlock Margin="30,10,30,30" Text="{Binding TextContent2}" TextWrapping="Wrap" Foreground="#FF606060" FontSize="17" />
</Grid>
</StackPanel>
</Grid>
</UserControl>
用户控件类:(ImagePage.xaml.cs)
private static void OnTitleChanged(DependencyObject d, DependencyPropertyChangedEventArgs e){
StackPanel stackPanel = (StackPanel)d;
stackPanel.Visibility = Visibility.Collapsed;
}
public string TextContent1
{
get { return (string)GetValue(TextContent1Property); }
set { SetValue(TextContent1Property, value); }
}
public static readonly DependencyProperty TextContent1Property =
DependencyProperty.Register("TextContent1", typeof(string), typeof(ImagePage), new PropertyMetadata("", new PropertyChangedCallback(OnTextContent1Changed)));
private static void OnTextContent1Changed(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
// what I want to do is if TextContent1 or TextContent2 has no value
// turn the stackpanel visibility to collapsed
StackPanel stackPanel = (StackPanel)d;
stackPanel.Visibility = Visibility.Collapsed;
}
除OnTextContent1Changed未触发外,其他一切工作正常! 所以我不知道这是否是正确的处理方式,但基本上我只是想根据用户输入的数据绑定将用户控件中的UI元素打开或关闭。
TextBlock
没有DataContext来查找DependencyProperty
。 如果在ImagePage.xaml中为Grid
命名:
<Grid Background="#FFF0F0F0" Margin="4,0" x:Name="MyGrid">
然后,可以在ImagePage.xaml.cs的ImagePage
构造函数中设置其DataContext:
public ImagePage()
{
InitializeComponent();
MyGrid.DataContext = this;
}
告诉Grid
(及其后代)在ImagePage
类上查找依赖项属性。 这样,Dependency属性应该正确绑定。 另外一个问题,不过,是你告诉DependencyProperty
,这是上ImagePage
与typeof(ImagePage)
但随后铸造一个StackPanel,将每一次失败:
StackPanel stackPanel = (StackPanel)d; // Throws System.InvalidCastException
您可以通过为StackPanel命名并直接在.cs文件中引用它来解决此问题。
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